Is it common for the expansion tank to leak on these? It has cracked 2 times before and I have patched it and has held but just seems to pop a new leak in another area a few months later. Is this due to the engine running too hot or do they just break down from the heat and pressure? I changed my tstat a few years ago and flushed it when I changed the water pump 4 months ago. I have a new expansion tank on the way and I guess I will order a new tstat as well. I am going to replace the throttle body heater tomorrow. When changing the throttle body heater Im also going to change the gasket on the throttle body, do I need to apply any sealant to the gasket for the heater or throttle body or will it just bolt tight?

 

Coolant jug plastic breaks down, one leak soon becomes another. However, the vent cap is arranged for like 18 PSI. If you are venting, there are other cooling system issues. Might want to change that cap as well. Tstat is good idea. A little Hylomar or such is OK for gasket assembly, low PSI (less than 20) and radiator level heat. May be fine with just gasket.

 

If you bottle has cracked then replace it, using some form of glue wont't fix it and it will blow again and possibly take your engine with it from an over heat.

 

And in case I was not clear, I was hinting that if it keeps springing a leak, maybe the pressure is too much because something else is going off the edge. However, in the hands of a non-tech driver, quick failure of coolant jug might well result in the "well I was going 75 on the expressway and I needed to get to the next exit with a gas station, it was only 12 miles" tale of woe from SHMBO or offspring.